Department of Biomolecular Engineering, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259-B-59 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa 226-8501, Japan.
J Am Chem Soc. 2009 Mar 11;131(9):3166-7. doi: 10.1021/ja809826a.
When arylmethyl 4-(sulfonyl)-3-butynyl ether and a catalytic amount of Rh(2)(tfa)(4) (tfa = CF(3)CO(2)-) were heated in toluene, 2-aryl-3-(sulfonyl)-5,6-dihydro-2H-pyran was produced in good yield. Ring closure proceeded in a highly regioselective manner, and no isomeric five-membered product was detected. Alternatively, 2-(5-sulfonyl-4-pentynyl)tetrahydrofuran lacking a benzyl substituent afforded a different product, 9-sulfonyl-1-hydroxy-8-nonen-4-one, upon reaction with the same rhodium catalyst at reflux in wet toluene. Both reactions most likely involve cleavage of the C-H bond alpha to ether in the substrate and subsequent intramolecular transfer of the hydrogen atom to sulfonylacetylene, which is supported by experiments using deuterium-labeled starting materials.
当芳基甲基 4-(磺酰基)-3-丁炔基醚和催化量的 Rh(2)(tfa)(4)（tfa = CF(3)CO(2)-）在甲苯中加热时，可得到高产率的 2-芳基-3-(磺酰基)-5,6-二氢-2H-吡喃。环闭合以高度区域选择性的方式进行，并且没有检测到异构的五元产物。或者，缺乏苄基取代基的 2-(5-磺酰基-4-戊炔基)四氢呋喃在相同的铑催化剂存在下，在回流的湿甲苯中反应，得到不同的产物 9-磺酰基-1-羟基-8-壬烯-4-酮。这两种反应最有可能涉及到底物中醚的α位 C-H 键的断裂，以及随后氢原子向磺酰基乙炔的分子内转移，这一假设得到了使用氘标记的起始原料进行实验的支持。
